BR102021007002A2 - SECONDARY TARGET RADAR - Google Patents

Abstract

secondary target radar. The radar comprises an antenna having a radiation pattern forming a sum channel, sum, a radiation pattern forming a difference channel, diff, and a pattern forming a control channel, cont, a first transmission and reception chain (4 ) being associated with the sum channel and a second transmission and reception chain (4') being associated with the cont channel, a reception channel (4) being associated with the diff channel. each of said transmission and reception chains (4, 4') is capable of transmitting and receiving simultaneously, the transmission chain (401) comprising a filtering operation (4a, 4b) that filters signals transmitted at 1090 MHz and the reception chain (402) comprising a filtering operation (4c, 4d) that filters signals transmitted at 1030 MHz, so that said chains operate independently of each other.

Description

SECONDARY TARGET RADAR

[001] The present invention relates to the field of air traffic control (ATC).

[002] Currently, air control is mainly based on secondary radar, whose detection reliability is widely recognized, secondary radar ensuring synchronous mode surveillance of aircraft according to SSR and Mode S protocols. Extended ADS-B (Automatic Dependent SurveillanceBroadcast) which are provided to ensure collision avoidance (TCAS: Traffic Alert and Collision Avoidance System) a onboard aircraft, it is operated in terrestrial ATC, thus delivering a part of the interactive surveillance system.

[003] This surveillance can be coupled with an IFF surveillance type (Identification Friend or Foe), IFF interrogators guaranteeing the identification of aircraft according to various military protocols.

• • Vigilância ATC para ambos alvos SSR, mas também no Modo S, com dois a três registradores BDS (Seletor de Dados commB, “commB Data Selector”) por avião a serem extraídos por vez, conforme convencionalmente exigido pelo usuário;
• • opcionalmente identificação IFF com protocolos cuja principal proteção militar consiste em sujeitar a resposta a um longo retardo variável, além da duração relacionada ao alcance, e que, portanto, requer, por natureza, um longo tempo de radiação de alvo;

– ou esguichos ADS-B civis ou esguichos Modo 5 militares devem ser ouvidos no modo assíncrono, esta operação de escuta:

• • sendo particularmente poluída pelas transmissões de interrogatório dos modos síncronos, cujas transmissões são numerosas, em particular no Modo S (pelo menos 2 e 3 interrogações por avião);
• • sendo associada a uma baixa probabilidade de detecção e decodificação na presença de muitos alvos devido à falta de seletividade azimutal, porque a operação de escuta de modo assíncrono é por natureza omnidirecional.

[004] Within a single structure grouping these sensors together, the operational use of these various activities simultaneously requires:
- the secondary radar and the IFF interrogator, if used, must be heard simultaneously, these modes suffering from a limitation of the time spent on the target, in order to guarantee, separately in time:

• • ATC surveillance for both SSR targets, but also in Mode S, with two to three BDS registers (commB Data Selector, “commB Data Selector”) per aircraft to be extracted at a time, as conventionally required by the user;
• • optionally IFF identification with protocols whose main military protection is to subject the response to a variable long delay, in addition to the range-related duration, and which therefore requires, by nature, a long target radiation time;

– either civilian ADS-B nozzles or military Mode 5 nozzles must be heard in asynchronous mode, this listening operation:

• • being particularly polluted by interrogation transmissions from synchronous modes, which transmissions are numerous, particularly in Mode S (at least 2 and 3 interrogations per plane);
• • being associated with a low probability of detection and decoding in the presence of many targets due to the lack of azimuthal selectivity, because the asynchronous listening operation is omnidirectional in nature.

[005] By way of example, considering 1200 aircraft per antenna rotation with an extraction of two BDS per target and a re-interrogation rate of about 1.5 (related to various external factors such as distorted responses, transponder occupancy, target movement, etc.), ie 3600 interrogations of ~20 µs (duration taken from Annex 10 of ICAO Vol IV), distortion duration due to synchronous interrogations only is about 140 µs for Mode S responses extended, that is, 504 milliseconds are polluted by 4 seconds of antenna rotation, this corresponding to about 13% of the duration of the listening operation. Specifically, because of its operation in synchronous mode, a secondary radar does not require any isolation between its transmit chain and its receive chain, as they operate at different times; as a result, conventionally, transmission leaks have a level in the receive chain close to the highest magnitude responses normally expected from an airplane, thus making any simultaneous listening operations impossible during interrogation. Thus, in existing radars, disturbances due to synchronous transmissions necessarily limit the probability of detection of ADS-B splashes to less than 87% (this maximum does not take into account all other possible environmental reasons for non-detection, such as splash response and distortion ADS-B, multipath, etc.).

[006] Furthermore, an ATC secondary radar antenna is designed to operate in synchronous mode with targets in the plane of normal relative to the main antenna panel; as a result, its 360-degree electromagnetic coverage, which is required for asynchronous listening, has limitations that we'll describe in detail below.

[007] To avoid these difficulties, the prior art, which is, for example, disclosed in documents FR 3 019 905 A1 and FR 2 658 967 A1, keeps these various activities separate in order to ensure the best possible performance, being the architecture suited to the specifics of each activity. Thus, conventional ADS-B reception generally consists of two rear antennas with 180° rear associated with two independent receivers, in order to ensure better detection than with a single 360° omnidirectional antenna, whose antennas are distinct from the radar antenna when are in the same place. Furthermore, IFF identification is most often performed at the expense of Mode S surveillance in the antenna rotation and the sector involved by the IFF identification due to the lack of dwell time to perform the 2 simultaneously in the azimuth necessary for the IFF identification.

[008] Consequently, the implementation of all these surveillance and identification activities generates high operating and maintenance costs. In particular, you need to take into account acquisition costs, infrastructure costs, ownership costs and network costs.

• - cada uma das referidas cadeias de transmissão e recepção é capaz de transmitir e receber simultaneamente, a cadeia de transmissão compreendendo uma operação de filtragem que filtra os sinais transmitidos a 1090 MHz e a cadeia de recepção compreendendo uma operação de filtragem que filtra os sinais transmitidos a 1030 MHz, e a referida cadeia de recepção associada ao canal DIFF compreendendo uma operação de filtragem que filtra sinais transmitidos a 1030 MHz, de tal forma que as referidas cadeias operam independentemente umas das outras, o nível de sinal de lado de recepção permanecendo inalterado durante uma transmissão de interrogação síncrona;
• - os meios de processamento compreendem o casamento de bandas de frequência do lado de recepção com os recursos de cada um dos protocolos de transação usados;
• - as referidas cadeias de recepção dos canais SUM, DIFF e CONT, respectivamente, são capazes de ouvir simultaneamente no modo síncrono e assíncrono os sinais recebidos dos alvos através dos padrões SUM, DIFF e CONT, respectivamente, as referidas operações de escuta no modo síncrono e assíncrono sendo independentes uma da outra, o nível de sinal de lado de recepção permanece inalterado durante uma transmissão de interrogação síncrona.

[009] An aim of the invention is especially to obtain a low-cost integrated interrogation and surveillance system, offering a performance almost comparable to stand-alone systems. To this end, the object of the invention is a secondary radar comprising an antenna having a radiation pattern forming a sum channel, designated SUM, a radiation pattern forming a difference channel, designated DIFF, and a pattern forming a control channel , designated CONT, a first transmission and reception chain being associated with the SUM channel and a second transmission and reception chain being associated with the CONT channel, a receive chain being associated with the DIFF channel, in this radar:

• - each of said transmission and reception chains is capable of transmitting and receiving simultaneously, the transmission chain comprising a filtering operation that filters the transmitted signals at 1090 MHz and the receiving chain comprising a filtering operation that filters the transmitted signals at 1030 MHz, and said receive string associated with the DIFF channel comprising a filtering operation that filters signals transmitted at 1030 MHz, such that said strings operate independently of each other, the receive side signal level remaining unchanged during a synchronous poll transmission;
• - the processing means comprise the matching of frequency bands on the receiving side with the resources of each of the transaction protocols used;
• - said reception chains of the SUM, DIFF and CONT channels, respectively, are able to hear simultaneously in synchronous and asynchronous mode the signals received from the targets through the SUM, DIFF and CONT standards, respectively, said listening operations in synchronous mode and asynchronous being independent of each other, the receive-side signal level remains unchanged during a synchronous polling transmission.

[0010] In a particular modality, said CONT pattern being composed of a frontal radiation pattern forming a channel designated CONT_Front and a rear radiation pattern forming a channel designated CONT_Back, said patterns CONT_Front and CONT_Back are processed separately in such a way that each of these transmission and reception chains are applied to the CONT_Front channel and the CONT_Back channel.

• - um primeiro remendo para preencher o orifício de detecção em elevação denominado cone de silêncio;
• - um segundo remendo para preencher o orifício de detecção no azimute 90 °;
• - um segundo remendo para preencher o orifício de detecção no azimute -90 °.

[0011] Said radar, for example, comprises a kit to extend the radiation pattern of the CONT_Back channel, which is placed at the back of said antenna, said kit comprising three radiation patches:

• - a first patch to fill the detection hole in elevation called the silence cone;
• - a second patch to fill the detection hole at azimuth 90°;
• - a second patch to fill the detection hole at azimuth -90°.

[0012] Each of said example transmission chains comprises dedicated filtering operations to reject eddy signals transmitted at 1090 MHz.

[0013] Each of said example receive chains comprises dedicated filtering operations to reject stray signals at 1030 MHz from the transmission channel.

[0014] In the case where it has ATC surveillance mission as its mission, said radar, for example, performs simultaneous listening operations through said standards separately for ADS-B Nozzles and independently of synchronous transactions.

[0015] In the case where its mission is to identify IFF, that radar, for example, performs synchronous IFF detections, independently of the synchronous SSR and Mode S operations.

[0016] In the case where its mission is to identify IFF, that radar, for example, performs simultaneous listening operations through said patterns separately for Nozzles Mode 5 Level 2, regardless of synchronous transactions.

[0017] In the case where its mission is to control the air environment, said radar, for example, performs simultaneous listening operations through said standards separately for any type of secondary responses, regardless of synchronous transactions.

[0018] Said radar transmits successively in periods of interrogation of general call ("all call") and periods of interrogation of specific call ("roll call"), specific call interrogations ("roll call") begin, for example , in all call interrogation periods.

[0019] Said radar transmitting successively in periods of interrogation of general call ("all call") and periods of interrogation of specific call ("roll call"), the general call listening operations ("all call") initiated in “all call” periods, for example, continue into specific “roll call” periods.

[0020] Other features and advantages of the invention will become evident with the aid of the description that follows, made in relation to the attached drawings that show:
Figure 1a is a diagram of an exemplary embodiment of a conventional secondary radar;
Figure 1b is a diagram of an exemplary embodiment of a radar in accordance with the invention;
Figure 2a, possible steps for implementing the invention;
Figure 2b, an example of sequences of transactions executed by a radar according to the prior art;
Figure 2c, an example of transaction sequences executed by a radar according to the invention;
Figure 3 is an illustration of one of the steps mentioned above;
Figure 4a, a presentation of the gains of 3 SUM, CONT_Front and CONT_Back antenna patterns as a function of the azimuth between +/- 180°;
Figure 4b, a presentation of the contribution of the extension of the CONT_Back pattern in azimuth according to the invention;
Figure 4c, a presentation of the gains of 3 SUM, CONT_Front and CONT_Back antenna patterns as a function of elevation from -60° to +180°;
Figure 4d, a presentation of the contribution of the extension of the CONT_Back pattern in elevation according to the invention;
Figure 5, transaction management of general call ("all call") and specific call ("roll call") according to the prior art;
Figure 6, an example of transaction management of general call ("all call") and specific call ("roll call") in a radar according to the invention;
Figure 7, another example of transaction management on a radar according to the invention;
Figure 8a, diagram of a kit to extend the CONT_Back pattern of an ATC secondary antenna;
Figure 8b, the implementation principle of the kit to extend the CONT_Back pattern on an ATC secondary antenna.

• - radar secundário convencional: garantindo vigilância de modo síncrono de aeronaves de acordo com os protocolos SSR e Modo S;
• - Interrogador IFF garantindo a identificação da aeronave de acordo com os protocolos Modo 4 e Modo 5;
• - receptor assíncrono de esguicho ADS-B estendido (DF17 / 18);
• - receptor assíncrono de esguicho Modo 5 Nível 2; além de explorar a mesma estrutura aérea (rotação, antena, motores, junta rotativa, cabos, etc.) e a mesma infraestrutura.

[0021] To reduce the various costs mentioned in the introduction, the present invention proposes a certain system, which will be called secondary goal sensor of full duplexing, which groups all the activities of sensors in the ground:

• - conventional secondary radar: ensuring synchronous surveillance of aircraft according to SSR and Mode S protocols;
• - IFF interrogator ensuring aircraft identification according to Mode 4 and Mode 5 protocols;
• - extended ADS-B asynchronous nozzle receiver (DF17 / 18);
• - Mode 5 Level 2 asynchronous nozzle receiver; in addition to exploring the same aerial structure (rotation, antenna, engines, rotating joint, cables, etc.) and the same infrastructure.

[0022] The solution approach provided by the invention is therefore in a context of resources common to these various activities within the secondary goal sensor, to explore the specifics of these activities in order to orthogonalize them. Orthogonalizing means making them independent of each other and thus obtaining the same performance for each of them, whether they are operating alone or all activated simultaneously.

• - transmite e recebe simultaneamente os vários sinais, garantindo uma total independência das tarefas de transmissão e recepção, explorando o aspecto de duas frequências que é característico do radar secundário (transmissão a 1030 MHz e recepção a 1090 MHz): o termo “duplexação completa” será usado abaixo para se referir a um modo de operação no qual a transmissão e a recepção são simultâneas;
• - realiza uma operação de filtragem adaptada às características de cada protocolo utilizado, ou seja, uma operação de filtragem que permite processar apenas a banda de frequência que contém o sinal útil, conforme ilustrado na Figura 1b, que é descrita a seguir;
• - escuta em modo síncrono, com a finalidade de realizar simultaneamente vigilância ATC (em SSR e em Modo S) e identificação IFF (em modos criptografados militares);
• - escuta em modo assíncrono através dos vários padrões de antena fisicamente disponíveis (ou seja, dependendo da arquitetura da antena), mas também melhora os recursos de irradiação do radar em relação à operação de escuta em modo assíncrono apenas para garantir uma melhor cobertura em altitude elevada e uma operação de escuta temporal de quase 100% no azimute.

[0023] The sensor targets like this:

• - transmits and receives the various signals simultaneously, ensuring total independence of transmission and reception tasks, exploring the two-frequency aspect that is characteristic of secondary radar (1030 MHz transmission and 1090 MHz reception): the term "complete duplexing" will be used below to refer to a mode of operation in which transmission and reception are simultaneous;
• - performs a filtering operation adapted to the characteristics of each protocol used, that is, a filtering operation that allows processing only the frequency band that contains the useful signal, as illustrated in Figure 1b, which is described below;
• - listening in synchronous mode, with the purpose of simultaneously performing ATC surveillance (in SSR and in Mode S) and IFF identification (in military encrypted modes);
• - asynchronous listening through the various physically available antenna patterns (ie depending on the antenna architecture), but also improves radar irradiation capabilities compared to asynchronous listening operation just to ensure better altitude coverage high and an almost 100% temporal listen operation at azimuth.

• • caso contrário, seu potencial de resposta é consumido desnecessariamente;
• • caso contrário, poluição é criada, ou seja, essas respostas constituem poluição para os outros radares, em particular aqueles mais próximos do alvo.

[0024] The "full duplex" operation according to the invention therefore allows:
- asynchronous listening operations are performed (ADS-B nozzles or 5 Level 2 mode) without suffering disturbances due to synchronous emissions;
- within the Mode S protocol, the duration of the roll call transaction sequences (in the so-called roll call periods (RC)) must be optimized and therefore the lower limit of the dwell time on targets should be shortened, this being particularly important, though not exclusively, in the case of high-speed rotating radar (typically 4 seconds per antenna rotation is conventional in an airport configuration, for example (see Figure 6) );
- regardless of the RC optimization, the targets to be detected as they enter the radar's electromagnetic band without disturbing the operational performance of the radar, that is, without modifying the duration of the general call periods dedicated to this purpose (see Figure 7) , then allowing these incoming targets to be blocked first to remove the DF11 responses they generate after the UF11 interrogations of this radar

• • otherwise, your response potential is needlessly consumed;
• • otherwise, pollution is created, that is, these responses constitute pollution for other radars, in particular those closer to the target.

[0025] The filtering operation combined with each protocol employed allows, at the receiver, an analysis band to be obtained that is as wide as necessary, and which is completed by these filtering operations combined with the useful signal band of each protocol ( this is both for its modulation spectrum, but also for the frequency stability of the transponder carrier), allowing the noise level to be lowered and thus allowing the detection threshold to be lowered in order to process more signals. weak and therefore further improve the range.

• • uma cobertura temporal a ser garantida para a operação de escuta de modo síncrono de cerca de 75% a média distância (ver Figura 4a),
• • esguichos simultâneos serem melhor detectados explorando sua diferença no ângulo de visão externa, se houver, para diminuir o grau de sobreposição das respostas (que são bastante longas (120 µs)), o que é uma causa da não detecção de esguichos,

- além disso, por completar o padrão de radiação da antena secundária ATC do radar, no que diz respeito à sua função de detecção de modo assíncrono:

• • cobertura no cone de silêncio (Cos) ser assegurada (ver Figura 4d);
• • uma cobertura temporal de 100% ao longo da distância máxima tanto em ADS-B como em IFF ser assegurada (ver Figura 4b).

[0026] The independent asynchronous mode operation of listening simultaneously through the three or four patterns of a conventional ACT antenna, therefore, allows:
- for processing receive side independently of SUM, DIFF, CONT_Front and CONT_Back patterns,

• • a temporal coverage to be guaranteed for the synchronous mode listening operation of about 75% at medium distance (see Figure 4a),
• • simultaneous splashes are better detected by exploiting their difference in the external viewing angle, if any, to decrease the degree of overlapping of the responses (which are quite long (120 µs)), which is a cause of non-detection of splashes,

- in addition, for completing the radiation pattern of the ATC secondary radar antenna, with regard to its detection function asynchronously:

• • coverage in the cone of silence (Cos) is ensured (see Figure 4d);
• • 100% temporal coverage over the maximum distance in both ADS-B and IFF is ensured (see Figure 4b).

[0027] The features and advantages of the invention presented above will be described below with reference to the figures.

[0028] Figure 1a will be remembered shows a diagram of a conventional ATC surveillance radar from which only synchronous mode operation in Mode S and SSR is expected. The 401, 402 transmit and receive chains have an isolation level just enough to guarantee non-destruction in the event of an infinite SWR at the output of the processing cabinet. The CONT_Front and CONT_Back patterns of the secondary ATC antenna are merged by antenna 1, 2 (CONT pattern), since any signals not exactly on the antenna axis, ie, the SUM axis, are simply rejected whether they come from the front or from behind.

[0029] Figure 1b shows a diagram of a device according to the invention. Through the proposed architecture, the properties of the “full duplexing” secondary meta sensor that were presented above are obtained. In particular, this architecture guarantees the simultaneous operation of the various secondary protocols with almost no influence between them. Thus, for each protocol, it is guaranteed that, by operating simultaneously with the other protocols, the same performance is achieved as would be possible in the structure of the sensor's antenna with the other protocols inactive. The architecture in Figure 1b is the evolution of the conventional secondary radar architecture shown in Figure 1a. Some of the descriptions below describe the components already present in the conventional radar in Figure 1a, with the additional elements highlighted through the use of thicker lines.

[0030] In its conventional operational configuration, the secondary radar operates in synchronous mode, that is, it issues an interrogation and waits for a response consistent with it, allowing it to locate through measurement (in terms of azimuth and distance) and identify (usually via an address in Mode S protocol) the target.

• ⚪ primeiro padrão de controle 13, denotado CONT_Front, para bloquear e rejeitar as respostas provenientes de alvos voltados para a antena e não presentes no feixe SUM principal;
• ⚪ segundo padrão de controle 14, denotado CONT_Back, para bloquear e rejeitar as respostas provenientes de alvos na parte traseira da antena (portanto, necessariamente não presente no feixe SUM principal).

No resto da invenção, esta configuração usando os padrões CONT_Front e CONT_Back é considerada, esses dois padrões possivelmente sendo processados separadamente. A referência ao canal CONT incluirá possivelmente os canais CONT_Front e CONT_Back em relação ao exemplo da Figura 1b.[0031] In order to perform this task effectively, the radar is equipped with an antenna 1 having a plurality of patterns 11, 12, 13, 14, whose functions are conventionally:
- the sum pattern 11, hereinafter denoted SUM, for interrogating and detecting the synchronous response of the target;
- 12 difference pattern, denoted DIFF, to accurately locate the target in the SUM beam;
- control pattern, denoted CONT (see Figure 1a), which can be advantageously split into two patterns in the context of an option of the invention (this option can therefore employ separate processing of the 3 or 4 antenna patterns):

• ⚪ first control pattern 13, denoted CONT_Front, to block and reject responses coming from targets facing the antenna and not present in the main SUM beam;
• ⚪ second control pattern 14, denoted CONT_Back, to block and reject responses from targets at the rear of the antenna (thus not necessarily present in the main SUM beam).

In the rest of the invention, this configuration using the CONT_Front and CONT_Back patterns is considered, these two patterns possibly being processed separately. The reference to the CONT channel will possibly include the CONT_Front and CONT_Back channels in relation to the example in Figure 1b.

• - Acoplamento RF dos sinais transmitidos a 1030 MHz e recebidos a 1090 MHz independentemente para os quatro padrões (SUM, DIFF, CONT_Front e CONT_Back) entre a parte rotativa e a parte fixa do radar;
• - a distribuição da posição azimutal 201 do eixo do lóbulo principal da antena.

[0032] A swivel joint 2 and antenna drop cables, for a swivel antenna, make sure to:

• - RF coupling of signals transmitted at 1030 MHz and received at 1090 MHz independently for the four standards (SUM, DIFF, CONT_Front and CONT_Back) between the rotating part and the fixed part of the radar;
• - the distribution of the azimuthal position 201 of the axis of the main lobe of the antenna.

[0033] A duplexer 3 ensures RF coupling between signals transmitted at 1030 MHz and received at 1090 MHz, independently for the four standards. For this purpose, the duplexer 3 comprises a circulator associated with each channel. In the example in Figure 1b, three circulators 311, 313, 314 decouple 1030 MHz transmission and 1090 MHz reception of the SUM, CONT_Front and CONT_Back channels, respectively. In purely synchronous operation, the listening operation is performed exclusively through the main lobe of the radar, that is, through the SUM and DIFF channels, after the transmission phase through the SUM and DIFF channels. As the DIFF channel operates only in reception, the pump 312 only operates in one direction, forwarding only the reception signals obtained through the antenna (the pump is optional, its use in DIFF has no other purpose than to balance the signals between SUM and DIFF with a view to measuring the error of the angle). In synchronous mode, the operation of listening through the CONT channel has no other purpose than to reject the responses received with more energy in the CONT pattern than in the SUM pattern.

[0034] Filters 311', 313', 314' are placed upstream of the pumps in the SUM, CONT_Front and CONT_Back channels. These filters are mainly used in transmission to filter harmonics from transmitted signals. The same filters also serve in reception to protect from frequencies outside the useful band of the secondary radar (ie around 1020 to 1100 MHz).

• - a arquitetura dos circuitos de transmissão e recepção 4' do canal CONT (Figura 1a) e do canal CONT_Front / CONT_Back (Figura 1b) sendo análogas à de SUM, respectivamente.
• - os circuitos 4” do canal DIFF não são ilustrados e são idênticos aos da recepção de SUM

[0035] The SUM and CONT channels are therefore used for both transmission and reception. For readability reasons, only the transmit and receive circuits 4 of the SUM channel were shown in Figure 1b (and in Figure 1a) (the circuits being the same for the CONT channel, or the CONT_Front and CONT_Back channels):

• - the architecture of the 4' transmission and reception circuits of the CONT channel (Figure 1a) and of the CONT_Front / CONT_Back channel (Figure 1b) being analogous to that of SUM, respectively.
• - the 4” circuits of the DIFF channel are not illustrated and are identical to those for SUM reception

[0036] The space-time management 5 guarantees the real-time management of the interrogation periods and associated listening periods of the various secondary protocols: IFF, SSR and Mode S protocols. The protocol-specific signal processing 6 exploits the obtained signals through the various SUM, DIFF, CONT_Front and CONT_Back patterns separately.

[0037] Again with reference to Figure 1b, the transmit and receive portion 4 that is associated with the SUM channel and located between the circulator 311 of the doubler and the space-time management 5 and the signal processing 6 will now be described. This transmit/receive portion 4 comprises specific adaptations of the invention. In particular, the SUM 401 transmission chain, which transmits at 1030 MHz, incorporates additional filtering operations 4A, 4B which are dedicated to decreasing transmission noise and more particularly to rejecting stray signals at 1090 MHz in order to maintain the noise residue level, after coupling 311, to the receiver noise level. The transmission chain comprises a first amplifier 8 which performs a first amplification; is followed by a first 4A filter. The latter is followed by a second amplifier 8', which is a power amplifier, and which supplies the transmission signal, this amplifier being followed by the second filter 4B.

• - selecionar sinais de recepção na banda de frequência de cerca de 1090 MHz;
• - rejeitar fortemente a banda de frequência de cerca de 1030 MHz originada da cadeia de transmissão. A configuração da Figura 1b é uma modalidade exemplar particular compreendendo um oscilador local (LO) 10 (oscilando a 1030 MHz) que é compartilhado entre o canal de transmissão 401 e o canal de recepção 402.

[0038] The receive chain SUM 402, which operates at 1090 MHz, conventionally comprises a low noise amplifier 9 and an analogue-digital converter (ADC) 9'. It also comprises specific adaptations of the invention, such as the transmission chain, and in particular additional 4C, 4D filtering operations dedicated to the rejection of stray signals, at 1030 MHz, coming from the transmission channel, in order to maintain the coupling level in the circulator (or due to air SWR) and poor baseband identification in the noise level of the receiver. In particular, the receive channel comprises an input filter 4C, upstream of the low noise amplifier 9. This filter, which is a bandpass filter, is intended for:

• - select receive signals in the frequency band around 1090 MHz;
• - strongly reject the frequency band of around 1030 MHz originating from the transmission chain. The configuration of Figure 1b is a particular exemplary embodiment comprising a local oscillator (LO) 10 (oscillating at 1030 MHz) that is shared between transmit channel 401 and receive channel 402.

[0039] In the transmission channel, upstream of the first amplifier 8, the transmission signal is modulated by a modulator 12 at the frequency of the local oscillator 10, that is, in 1030 MHz. A filter 4E is inserted between the oscillator and the modulator and is intended to filter noise at 1090 MHz. In the receive channel, before analogue-digital conversion 9', the received signal is mixed with the local oscillator signal by a mixer 11, then filtered by a pass filter -band 13. A 4D filter is placed on the output of the ADC 9' to filter the signal at 1030 MHz.

[0040] The DIFF channel, which operates only in reception, comprises an analogue of the receive chain to the receive chain 402 of the SUM channel; in particular, it comprises the 4C, 4D filtering operation which filters the signals transmitted at 1030 MHz. All transmission and/or reception chains SUM, DIFF and CONT operate independently of each other.

[0041] The four civil ATC antenna standards are processed separately, requiring a 4-channel receiver (or 3-channel receiver if CONT_Front and CONT_Back are merged into a single CONT as is usually the case and as illustrated in Figure 1a).

[0042] Before any decoding of the responses, each signal processing operation 6 independently combines its analysis band with the resources of the protocol whose responses it detects. This filtering operation coupled with each protocol used allows a better performance to be obtained by decreasing the noise level, thus allowing the detection threshold to be lowered independently for each protocol to process weaker signals.

[0043] Figure 2a illustrates the steps of implementing the invention. At least two steps are required for this implementation.

• • BW_IFF > BW_SSR > BW_MS > BW_ADS-B, onde BW_IFF, BW_SSR, BW_MS e BW_ADS-B são as larguras de banda IFF, SSR, Modo S e ADS-B, respectivamente.
• - por ouvir, em modo assíncrono, simultaneamente:
• • através do maior número de padrões independentes que existem em um radar secundário;
• • opcionalmente 214, os padrões CONT_Front e CONT_Back podem ser processados separadamente;
• • também opcionalmente 215, um kit para estender o lado de recepção do padrão CONT_back apenas para garantir a cobertura de RF em alta elevação e que seja completa em 360 ° do azimute pode ser empregado.

[0044] The first step 21 allows a conventional Mode S secondary radar to be converted into a "full duplexing" secondary target sensor according to the invention. In this step 21, the various protocols are orthogonalized and the radar is suitable for asynchronous reception. The orthogonalization here consists of making the processing operations of the protocols completely independent. In practice, the orthogonalization of protocols is achieved:
- at 211 in the 1090 MHz receive chain, via rejection of interrogations at 1030 MHz in the noise level of the 1090 MHz chain, as illustrated by filters 4C, 4D of Figure 1b;
- at 212 in the 1030 MHz transmission chain, by rejecting the signal transmitted at 1090 MHz below the reception noise of 1090 MHz, as illustrated by filters 4A, 4B of Figure 1b;
- reception side, as the analysis bands (BeamWidth_BW) correspond 213 to the characteristics of the protocols used, in particular that:

• • BW_IFF > BW_SSR > BW_MS > BW_ADS-B, where BW_IFF, BW_SSR, BW_MS, and BW_ADS-B are the IFF, SSR, Mode S, and ADS-B bandwidths, respectively.
• - by listening, in asynchronous mode, simultaneously:
• • through the greater number of independent patterns that exist in a secondary radar;
• • optionally 214, the CONT_Front and CONT_Back patterns can be processed separately;
• • also optionally 215, a kit to extend the receiving side of the CONT_back pattern just to ensure RF coverage at high elevation and which is complete at 360° of azimuth can be employed.

• • por ouvir simultaneamente em modo assíncrono através dos três ou quatro padrões separadamente para esguichos ADS-B, independentemente das atividades síncronas;
• • por otimizar a duração das sequências de transações de chamada específica (“roll call”) com nenhuma outra restrição importante do que a não sobreposição dos períodos de escuta, a fim de evitar a "distorção de resposta" e a não sobreposição das interrogações (por natureza alcançada devido à singularidade do transmissor), e fazê-lo com períodos de escuta de chamada específica (“roll call”) simultâneos com períodos de transmissão de chamada geral (“all call”);

- no campo do controle aéreo militar 24 ou identificação IFF:

• • através do interrogador IFF, que realiza suas transações de identificação tendo como única restrição o acesso ao recurso de transmissão compartilhado com a vigilância SSR / Modo S;
• • por ouvir simultaneamente através dos três ou quatro padrões separadamente para esguichos Modo 5 Nível 2, independentemente das atividades síncronas;

- no campo do controle do ambiente aéreo 25:

• • por ouvir simultaneamente através dos três ou quatro padrões separadamente para qualquer tipo de resposta secundária (incluindo respostas falsas não sincronizadas no tempo (FRUITs), independentemente das atividades síncronas.

[0045] In the second step 22, the orthogonalization of the protocols is operationally explored:
- in the field of civil air control 23 or ATC surveillance:

• • by simultaneously listening in asynchronous mode through the three or four patterns separately for ADS-B nozzles, regardless of synchronous activities;
• • by optimizing the duration of specific call transaction sequences ("roll call") with no other important restriction than non-overlapping listen periods, in order to avoid "response distortion" and non-overlapping interrogations ( by nature achieved due to the uniqueness of the transmitter), and to do so with periods of specific call listening (“roll call”) simultaneous with periods of general call transmission (“all call”);

- in the field of military air control 24 or IFF identification:

• • through the IFF interrogator, which carries out its identification transactions with the sole restriction of access to the transmission resource shared with SSR / Mode S surveillance;
• • by simultaneously listening through the three or four patterns separately for Mode 5 Level 2 squirts, regardless of synchronous activities;

- in the field of air environment control 25:

• • by simultaneously listening through the three or four patterns separately for any type of secondary response (including time-synchronized false responses (FRUITs), regardless of synchronous activities.

• - período N + 2: chamada geral (“all call”) (AC), dedicada a transações SSR e Modo S de chamada geral (“all call”);
• - período N + 3: chamada específica (“roll call”) (RC), dedicada a transações de modo S de chamada específica (“roll call”);
• - período N + 1: IFF, dedicado ao modo militar. Se o tempo de permanência no alvo permitir, o radar é capaz, na melhor das hipóteses, de intercalar os períodos de acordo com a sequência acima ilustrada na Figura 2b. Se o tempo de permanência não permitir, ou seja, a velocidade de rotação de antena for alta (o caso mais comum), o radar realiza então identificações IFF militares em detrimento da vigilância civil, os três períodos não podendo ocorrer no tempo de permanência disponível.

[0046] Figures 2b and 2c illustrate the sequencing of the IFF and SSR / Mode S interrogations for a radar according to the prior art and for a radar according to the invention, respectively. Figure 2b, therefore, illustrates the conventional operation, according to the prior art, by means of an example of sequencing of three successive periods:

• - period N + 2: general call (“all call”) (AC), dedicated to SSR and Mode S transactions of general call (“all call”);
• - period N + 3: roll call (RC), dedicated to roll call mode S transactions;
• - period N + 1: IFF, dedicated to military mode. If the target dwell time allows, the radar is capable, at best, of interleaving the periods according to the sequence illustrated above in Figure 2b. If the dwell time does not allow it, that is, the antenna rotation speed is high (the most common case), the radar then performs military IFF identifications at the expense of civil surveillance, the three periods cannot occur in the available dwell time .

• - detecção de IFF apesar das muitas transmissões de Modo S (ver períodos N + 1 e N + 3 na Figura 2c);
• - mas também a detecção de Modo S, apesar das poucas transmissões IFF (veja os períodos N + 1 e N + 2 na Figura 2c). Isso permite identificações militares IFF e vigilância civil simultâneas, mesmo com radares cuja velocidade de rotação é alta.

[0047] Figure 2c illustrates an example of operation according to the invention. In this case, transactions can overlap from one period to another and, in particular, IFF IDs can be extended to periods N + 2 and N + 3. Specifically, the radar according to the invention executes the transactions IFF at its own specific rate (which completely differs from that of SSR and Mode S transactions), regardless of the AC and RC periods, which are still devoted to Mode SSR and Mode S. This functional orthogonalization (see Figure 2a) exploits RF isolation transmission and reception (see Figure 1b), which allows for both:

• - IFF detection despite many Mode S transmissions (see periods N + 1 and N + 3 in Figure 2c);
• - but also Mode S detection, despite the few IFF transmissions (see periods N + 1 and N + 2 in Figure 2c). This allows simultaneous military IFF identifications and civilian surveillance, even with radars whose rotation speed is high.

[0048] Figure 3 illustrates an example of operational exploration, according to step 23 described above, and which optimizes ATC surveillance. This exploration example is illustrated with respect to three aircraft 31, 32, 33 present in the environment of a radar according to the invention. The ADS_B nozzles are heard simultaneously through the SUM pattern, through the DIFF pattern, through the CONT_Front pattern and through the CONT_Back pattern of the radar. These simultaneous listening operations allow the overlapping of asynchronous responses from targets located at different viewing angles to be avoided and thus their detection and decoding to be improved. The aircraft transmits the asynchronous ADS-B responses omnidirectionally 30. The response from a first aircraft 31 is thus received via the SUM pattern, the response from a second aircraft 32 is thus received via the CONT_Front pattern, and the response from a third aircraft 33 is thus received via the CONT_Back pattern. The ADS-B reception independent by default from the antenna allows, in this example, that these 3 nozzles are detected, although they are temporally simultaneous.

• - no seu plano principal, ou seja, a + 90 ° e -90 ° no azimute, a radiação é zero, o que não penaliza de forma alguma o funcionamento síncrono do radar normal ao plano desta antena,
• - no eixo da antena, o ganho de CONT_Front é intencionalmente atenuado no modo síncrono: esta queda intencional no ganho de CONT_Front sendo fornecida a fim de garantir uma diferenciação limpa em azimute entre ele e o feixe de radar no modo síncrono.

[0049] Figure 4a shows the pattern gains of a secondary conventional ATC antenna from Figure 1a as a function of azimuth. More precisely, Figure 4a quantifies, by means of a 360° graph (+/- 180° in relation to the antenna), the amplitude of the signals received from a given target depending on their azimuth in relation to the axis 40 of the radar antenna . In synchronous radar operation, the predominant pattern is SUM, which guarantees the transmission of useful queries and the reception of useful responses, while the role of the CONT_Front and CONT_Back patterns is to ensure that the side lobes are higher than the SUM pattern, that is, , to provide a relative gain to avoid false radar detections (from off-axis targets). In contrast, in asynchronous mode reception of ADS-B and IFF nozzles, the role of CONT_Front and CONT_Back is preponderant: their absolute gain defines the range of the ADS-B receiver and its 360° coverage is reflected in the temporal coverage of the operation. listening for squirts. In the average ADS-B band, the temporal coverage class of the listening operation performed via CONT_Front and CONT_Back is 75%, which is a consequence of the design of the conventional secondary ATC antenna, in which:

• - in its main plane, that is, at +90° and -90° in the azimuth, the radiation is zero, which in no way penalizes the synchronous operation of the radar normal to the plane of this antenna,
• - on the antenna axis, the CONT_Front gain is intentionally attenuated in synchronous mode: this intentional drop in CONT_Front gain being provided in order to ensure a clean differentiation in azimuth between it and the radar beam in synchronous mode.

[0050] Thus, listening through SUM (or even through DIFF), in addition to listening through CONT_Front, makes it possible to guarantee a temporal coverage of about 5%, by filling the drop in gain of the normal CONF_Front pattern to antenna plan. In general, listening in asynchronous mode independently and therefore simultaneously through two or three antenna patterns (SUM, CONT or SUM, CONT_Front, CONT_Back) makes it possible to ensure that the listening operation in asynchronous mode has coverage temporal of about 80% in the average ADS-B range, and this remains at least 50% in the maximum ADS-B range.

[0051] Figure 4b shows the complementarity of azimuthal radiation 41 of the CONT_Back pattern according to the invention. The goal is to ensure a 1090 MHz receive-side radiation pattern that has an equivalent level across the entire CONT coverage; thus, reception of ADS-B and IFF nozzles is guaranteed, in the maximum ADS-B and IFF range, with 100% temporal listening coverage.

• - convencionalmente, o padrão SUM tem um máximo (ver Figura 4a) de cerca de 15 a 20 dB maior do que CONT_Front;
• - os vazamentos 42 do padrão SUM do painel frontal, oposto ao normal ao plano da antena, são convencionalmente inferiores a -35dB.

[0052] Figure 4c shows the pattern gains of a secondary conventional ATC antenna from Figure 1a as a function of elevation. The pattern SUM, CONT_Front and CONT_Back are shown in it, each to its maximum azimuth:

• - conventionally, the SUM pattern has a maximum (see Figure 4a) of about 15 to 20 dB greater than CONT_Front;
• - the 42 leakages of the front panel SUM pattern, as opposed to normal to the antenna plane, are conventionally less than -35dB.

[0053] It can be seen that, by design, an ATC secondary antenna exhibits a very large drop in gain at high elevation, ie, beyond 50° at elevation. Consequently, secondary radars conventionally do not detect in a cone of silence (CoS) extending from 45° of elevation. The ADS-B function built into a radar and using the same antenna displays the same type of CoS.

[0054] Figure 4d shows the complementarity of radiation at elevation 43 of the CONT_Back pattern according to the invention. The objective is to ensure that there is a receive-side radiation pattern of 1090 MHz, even at very high altitudes (>85°), allowing ADS-B and IFF nozzles to be received through this extension of the CONT_Back pattern for high altitudes .

[0055] Figures 5 and 6 illustrate the advantages of the invention with regard to the sequencing of transactions of specific call ("roll call") and general call ("all call"). More precisely, Figure 5 shows the conventional sequencing employed with a radar according to the prior art, and Figure 6 shows the optimized sequencing with a radar according to the invention, in relation to the second step 22 described with reference to Figure 2a .

[0056] In Figure 5, the periods of all call transactions (AC) and roll call transactions (RC) follow one after the other in succession at a rate of 51, 52. By way of example, Figure 5 shows four successive periods of order m, m + 1, m + 2 in + 3 during a dwell time of the radar antenna lobe and corresponding successively to periods AC and RC. These AC and RC periods are separate, as are the transmit and receive phases they contain.

• - a duração dos períodos RC ser diminuída,
• - os períodos AC e RC serem intercalados (as operações de seletivamente escutar para o início do RC em períodos AC), e, portanto, o limite inferior do tempo de permanência em um alvo deve ser diminuído: o lóbulo da antena agora cobre sete fases AC ou RC (m a m + 6).

[0057] The rate 61, 62 of the AC and RC interrogations shown in Figure 6 and corresponding to a radar according to the invention is different. RC periods are shorter. In particular, the invention advantageously allows the duration of the specific call transaction sequences ("roll call") to be optimized, since it is possible to transmit or not the specific call transmissions ("roll call") during the listening phase roll call or all call. More particularly, the invention allows:

• - the duration of the RC periods be shortened,
• - AC and RC periods are interleaved (the operations of selectively listening for RC start in AC periods), and therefore the lower limit of dwell time on a target must be lowered: the antenna lobe now covers seven phases AC or RC (mam + 6).

[0058] Figure 7 shows another possibility with regard to the sequencing of the AC and RC periods for a radar according to the invention. The sequencing of the AC and RC periods is, for example, the same as in the case of Figure 5. To allow the planes to be managed before entering operational radar coverage, the RC 71 listening operation, which starts in the AC period, continues during the start of the RC transaction phase, which necessarily starts with interrogations (synchronous mode), and therefore no dwell time is lost in relation to the targets present in the operational coverage.

• - que consomem seu potencial de resposta desnecessariamente;
• - que poluem com suas respostas outros radares, em particular aqueles mais próximos do alvo.

[0059] The objective here is, regardless of the optimization of the previous RC periods (see Figure 6), to detect targets that are outside the operational range of the radar, but within its electromagnetic range, in order to decrease the number of DF11 responses that these targets generate in response to interrogations from this radar,

• - that consume their response potential unnecessarily;
• - that pollute other radars with their responses, in particular those closest to the target.

• - lado frontal, de um conjunto 80 de N colunas de P dipolos radiantes (formando os padrões SUM, DIFF e CONT_Front),
• - lado posterior, de uma coluna 90 de P dipolos radiantes, formando o padrão CONT_Back.

[0060] Figure 8a shows the diagram of a kit 215 to extend the 1090 MHz receive-side CONT_Back pattern (see Figure 2a) both in azimuth (about -90° and +90°), but also in elevation beyond of 50° elevation in the 3-pattern antenna configuration shown as an example. This kit 215 is added to the conventional structure of antenna 1, which is composed of:

• - front side, of a set of 80 N columns of radiant P dipoles (forming the SUM, DIFF and CONT_Front patterns),
• - back side, of a column 90 of radiant P dipoles, forming the CONT_Back pattern.

[0061] A distribution circuit 800, well known in the art, distributes the signals to the SUM, DIFF and CONT channels (CONT_Front and CONT_Back).

[0062] This kit to extend the CONT_Back pattern is intended to fill the detection holes specially illustrated in Figures 4a through 4d, as described below.

• - um 81 para preencher o cone de silêncio com uma inclinação no sentido da elevação de cerca de 110 ° em seu plano direcional e no azimute 180 °,
• - um segundo 82 para preencher o orifício de detecção direito no azimute 90 °, seu plano direcional tendo uma inclinação de elevação de cerca de 0 °,
• - um terceiro 83 para preencher o orifício de detecção esquerdo no azimute de -90 °, seu plano direcional tendo uma inclinação de elevação de cerca de 0 °.

[0063] In order not to disturb the synchronous operation of the radar, the extent of standard 215 is limited to the requirement, that is, with regard to the reception of ADS-B and IFF nozzles. The extension is placed opposite the front panel and therefore extends CONT_Back, as the exemplary modality shown in Figure 8b illustrates. The radiant portion of the extension kit is divided in a plane into 3 directional patches 81, 82, 83 (with a lobe on the order of +/- 35 °, for example):

• - an 81 to fill the cone of silence with an elevation inclination of about 110° in its directional plane and at azimuth 180°,
• - an 82 second to fill the right sensing hole at azimuth 90°, its directional plane having an elevation slope of about 0°,
• - a third 83 to fill the left sensing hole at azimuth of -90°, its directional plane having an elevation slope of about 0°.

[0064] The signals are routed between the distribution circuit and the column 90 (conventional CONT_Back) and the three patches 81, 82, 83, are carried out in a conventional way by a set of circulators, couplers and adders.

[0065] Figure 8b shows a possible arrangement of these radiating elements 81, 82, 83 according to the invention in a conventional ATC secondary antenna 1. The "right" patch 82 and the "left" patch 83 are each placed at a rear end of the antenna plane. Patch 81 assigned to the cone of silence is placed in the center, behind the antenna plane.

Claims (11)

Secondary radar comprising an antenna (1) having a radiation pattern forming a sum channel, designated SUM, a radiation pattern forming a difference channel, designated DIFF, and a pattern forming a control channel, designated CONT, a first chain of transmission and reception (4) being associated with the SUM channel and a second transmission and reception chain (4') being associated with the CONT channel, a receiving chain (4”) being associated with the DIFF channel, CHARACTERIZED by the fact that:

• - each of said transmission and reception chains (4, 4') is capable of transmitting and receiving simultaneously, the transmission chain (401) comprising a filtering operation (4A, 4B) which filters the transmitted signals in 1090 MHz and the receiving chain (402) comprising a filtering operation (4C, 4D) that filters the signals transmitted at 1030 MHz and said receiving chain (4") associated with the DIFF channel comprising a filtering operation (4C, 4D) that filters the signals transmitted at 1030 MHz such that said strings operate independently of each other, the receiving side signal level remaining unchanged during a synchronous polling transmission;
• - the processing means (6) comprise the correspondence of frequency bands on the receiving side with the characteristics of each of the transaction protocols used;
• - said reception chains of the SUM, DIFF and CONT channels, respectively, are capable of listening simultaneously in synchronous and asynchronous mode to the signals received from the targets through the SUM, DIFF and CONT standards, respectively, said listening operations in the synchronous and asynchronous mode being independent of each other, the receive side signal level remains unchanged during a synchronous poll transmission.

Secondary radar, according to claim 1, CHARACTERIZED by the fact that said CONT pattern is composed of a frontal radiation pattern forming a channel designated CONT_Front and a rear radiation pattern forming a channel designated CONT_Back, said patterns CONT_Front and CONT_Back they are processed separately in such a way that each of said transmission and reception chains (401, 402) is applied to the CONT_Front channel and to the CONT_Back channel. Secondary radar, according to claim 2, CHARACTERIZED by the fact that it comprises a kit to extend the radiation pattern of the CONT_Back channel, which is placed on the rear side of said antenna (1), said kit comprising three radiant patches:

• - a first patch (81) for filling the detection hole in elevation called the silencer cone;
• - a second patch (82) to fill the detection hole at azimuth 90°;
• - a third patch (83) to fill the sensing hole at azimuth -90°.

Secondary radar, according to any one of claims 1 to 3, CHARACTERIZED by the fact that each of said transmission chains comprises filtering operations (4A, 4B) dedicated to rejecting stray signals transmitted at 1090 MHz. Secondary radar, according to any one of claims 1 to 4, CHARACTERIZED by the fact that each of said reception chains comprises filtering operations (4C, 4D) dedicated to the rejection of stray signals at 1030 MHz from the transmission channel . Secondary radar, according to any one of claims 1 to 5, CHARACTERIZED by the fact that, having as its ATC surveillance mission (23), it performs simultaneous listening operations through said standards separately for ADS-B nozzles and independently of synchronous transactions . Secondary radar, according to any one of claims 1 to 6, CHARACTERIZED by the fact that, having as its mission the IFF identification, it performs synchronous IFF detections, independently of synchronous SSR and Mode S transactions. Secondary radar, according to any one of claims 1 to 7, CHARACTERIZED by the fact that, having as its mission the IFF identification, it performs simultaneous listening operations through said standards separately for Mode 5 Level 2 nozzles, regardless of synchronous transactions. Secondary radar, according to any one of claims 1 to 8, CHARACTERIZED by the fact that, having as its mission to control the air environment (25), it performs simultaneous listening operations through said standards separately for any type of secondary responses, independently of synchronous transactions. Secondary radar, according to any one of claims 1 to 9, CHARACTERIZED by the fact that said radar transmits successively in all call interrogation periods and roll call interrogation periods ), roll call interrogations (63) begin at all call interrogation periods. Secondary radar, according to any one of claims 1 to 10, CHARACTERIZED by the fact that said radar transmitting successively in periods of interrogation of general call ("all call") and periods of interrogation of specific call ("roll call" ), all call listening operations (71) initiated in all call periods continue in specific roll call periods.

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